Turning HDPE on the lathe?

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jrista

jrista

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I ordered some small 3" HDPE squares to make some zero-clearance plates for my Jet bandsaw. There are some third party plates on the market, but all of them seem to be 2.5" diameter, and by my caliper measure my lathe is 2.75". Additionally, the lip in the hole of my lathe is thinner than these third party plates.

I have the HDPE sheets, but I now have the problem of turning them. I've been trying to find a way to do that, and came across this video by Ed of ExoticBlanks:


His idea of using a nut bonded directly to a piece of wood is quite intriguing! The challenge I have now is, I'm having trouble getting any glue to stick...which, ironically, is kind of the point of HDPE! :p So now I'm on the hunt for a type of glue that will indeed bond to HDPE and hold it tightly enough that I could turn it round, and down to a diameter of 2.75" with a 1/8" thick lip about 3/16" wide.

Thanks!
 
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I have never done it myself, but I have heard that Gorilla brand hot melt glue works pretty good on plastics, but you might want to just give regular old hot glue a try. Glue it to a sacrificial wood disc/plate on the headstock and then use a 3/4 inch piece of dowel or something on the tailstock side to sandwich it in with the tailstock while you turn it down. - Dave.
 
Dave`s suggestions sound good to me . I hope the HDPE you have is a clear unfilled one . The grades used for farm machinery skid plates or grader blades will destroy a carbide tool edge very rapidly .
 
jrista said:
I ordered some small 3" HDPE squares to make some zero-clearance plates for my Jet bandsaw. There are some third party plates on the market, but all of them seem to be 2.5" diameter, and by my caliper measure my lathe is 2.75". Additionally, the lip in the hole of my lathe is thinner than these third party plates.

I have the HDPE sheets, but I now have the problem of turning them. I've been trying to find a way to do that, and came across this video by Ed of ExoticBlanks:


His idea of using a nut bonded directly to a piece of wood is quite intriguing! The challenge I have now is, I'm having trouble getting any glue to stick...which, ironically, is kind of the point of HDPE! :p So now I'm on the hunt for a type of glue that will indeed bond to HDPE and hold it tightly enough that I could turn it round, and down to a diameter of 2.75" with a 1/8" thick lip about 3/16" wide.

Thanks!
Click to expand...
https://gluefaq.com/how-to-glue-hdp...l,small or light objects, but not very strong.
 
jrista said:
I ordered some small 3" HDPE squares to make some zero-clearance plates for my Jet bandsaw. There are some third party plates on the market, but all of them seem to be 2.5" diameter, and by my caliper measure my lathe is 2.75". Additionally, the lip in the hole of my lathe is thinner than these third party plates.

I have the HDPE sheets, but I now have the problem of turning them. I've been trying to find a way to do that, and came across this video by Ed of ExoticBlanks:


His idea of using a nut bonded directly to a piece of wood is quite intriguing! The challenge I have now is, I'm having trouble getting any glue to stick...which, ironically, is kind of the point of HDPE! :p So now I'm on the hunt for a type of glue that will indeed bond to HDPE and hold it tightly enough that I could turn it round, and down to a diameter of 2.75" with a 1/8" thick lip about 3/16" wide.

Thanks!
Click to expand...
You can get very strong double sided tape which will probably work
 
jrista said:
I ordered some small 3" HDPE squares to make some zero-clearance plates for my Jet bandsaw. There are some third party plates on the market, but all of them seem to be 2.5" diameter, and by my caliper measure my lathe is 2.75". Additionally, the lip in the hole of my lathe is thinner than these third party plates.

I have the HDPE sheets, but I now have the problem of turning them. I've been trying to find a way to do that, and came across this video by Ed of ExoticBlanks:


His idea of using a nut bonded directly to a piece of wood is quite intriguing! The challenge I have now is, I'm having trouble getting any glue to stick...which, ironically, is kind of the point of HDPE! :p So now I'm on the hunt for a type of glue that will indeed bond to HDPE and hold it tightly enough that I could turn it round, and down to a diameter of 2.75" with a 1/8" thick lip about 3/16" wide.

Thanks!
Click to expand...
Attach a bit of MDF to a faceplate and stick the hdpe to that with the tape.
 
Yes, I believe some carpet tape would hold just fine. Attach to a piece of MDF and secure in a 4 jaw chuck or as others have said to a face plate and then attach that the HDPE to it and use your live center to keep pressure on it as you turn round and do the lip using either a parting tool, skew, or even carbide diamond tool.
 
jrista said:
I ordered some small 3" HDPE squares to make some zero-clearance plates for my Jet bandsaw. There are some third party plates on the market, but all of them seem to be 2.5" diameter, and by my caliper measure my lathe is 2.75". Additionally, the lip in the hole of my lathe is thinner than these third party plates.

I have the HDPE sheets, but I now have the problem of turning them. I've been trying to find a way to do that, and came across this video by Ed of ExoticBlanks:


His idea of using a nut bonded directly to a piece of wood is quite intriguing! The challenge I have now is, I'm having trouble getting any glue to stick...which, ironically, is kind of the point of HDPE! :p So now I'm on the hunt for a type of glue that will indeed bond to HDPE and hold it tightly enough that I could turn it round, and down to a diameter of 2.75" with a 1/8" thick lip about 3/16" wide.

Thanks!
Click to expand...
1644741004099.png
 
Something that has not been mentioned is what exactly is the shape of the item being turned. I get the impression that is is a round disk that is intended to fit into an opening in the table of a bandsaw. If that disk is to be solid, with the cutout for the bandsaw made later, then the approach I would take is to press the HDPE blanks against a wooden faceplate using pressure from a cone-type livecenter in the tailstock. If the HDPE blank slips (and it probably would), gluing a used sanding disk to the faceplate will provide additional grip. The tip of the live center will actually press into the HDPE and hold the blank in place. It would then be a simple matter to cut a disk using a thin parting tool or a skew chisel.

I have some Scotch mounting tape in my shop - and I would NEVER use it to mount anything on the lathe. It has a foam core that is just squishy enough to mean that a blank that is mounted with it will move. And my experience is that the foam core can tear easily. I do use a fabric-core carpet tape (Shurtape) for mounting - unlike the foam core in the Scotch product, the fabric in Shurtape is much thinner and won't compress significantly, and it's tear-strength is much greater. Shurtape could be used to mount HDPE - it might not bond to the HDPE as well as it does to wood or metal, but it would still be sticky and prevent the blank from rotating when held in place by a livecenter.

Another approach would be to use a faceplate that is larger than the blank. Again, use tailstock pressure to hold the blank against the faceplate, but put small blobs on hot-melt glue at the corners of the blank. The glue will adhere to the faceplate, but it may not stick to the HDPE - that's ok because it's only purpose is to prevent the blank from rotating as the lathe spins.

I've turned a lot of HDPE on my lathe - it cuts amazingly well with conventional turning tools I've used it to make a number of replacement tips for livecenters - because it's so slippery, it can apply pressure to a blank without actually gripping that blank, so it acts as a 'soft touch'. One of the problems is that ordinary glues won't adhere to it so gluing it to wood is a challenge. The approach I take to put an HDPE face on the end of a turning to make a 'soft touch' live center is to cut a mortise in the end of the wood blank, and then cut a tenon in the HDPE that fits fairly snugly into that mortise. I add a small groove on the side of the tenon, and the use epoxy to glue it into the mortise., making sure to use enough glue to completely fill that groove. The glue won't adhere to the HDPE, but it sticks very well to the wood, and it cures to create a hard ring on the walls of the mortise that mates with the groove on the tenon, locking the HDPE in place mechanically.
 
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jrista said:
I ordered some small 3" HDPE squares to make some zero-clearance plates for my Jet bandsaw. There are some third party plates on the market, but all of them seem to be 2.5" diameter, and by my caliper measure my lathe is 2.75". Additionally, the lip in the hole of my lathe is thinner than these third party plates.

I have the HDPE sheets, but I now have the problem of turning them. I've been trying to find a way to do that, and came across this video by Ed of ExoticBlanks:


His idea of using a nut bonded directly to a piece of wood is quite intriguing! The challenge I have now is, I'm having trouble getting any glue to stick...which, ironically, is kind of the point of HDPE! :p So now I'm on the hunt for a type of glue that will indeed bond to HDPE and hold it tightly enough that I could turn it round, and down to a diameter of 2.75" with a 1/8" thick lip about 3/16" wide.

Thanks!
Click to expand...
Ed's approach to making a sanding disk s fine, but there are other ways to skin this cat.

First, for a one-off project, buying a nut is probably practical. But if you anticipate doing something like this frequently (for faceplates, glueblocks, or other special fixings), it's less expensive to buy a tap that you can use to create threads in wood directly. Ace Hardware lists 1"x8tpi taps as standard warehouse items and can get them to a local store in a matter of days. They also typically have 3/4x16tpi taps in stock. Taps for larger lathes can be purchased from speciality suppliers such as Beale. I have a number of fixings that screw directly to the spindle of my lathe where the threads were cut in wood. My experience is that threads cut better and last long when cut into face grain. You can thread soft woods like pine, but I've found that harder woods work better - I prefer maple, ash or birch. Also, I drill the initial hole all the way through the blank and then tap the full depth of the hole. That way I only need a standard taper-tap and don't have the expense of a second 'bottoming tap' to complete the threads. After the mounting has been finished, I clean up the end and clue on another piece of timber on to make a working face. For added strength, I cut a male tenon on the outboard end of the threaded fixing, and put a matching female mortise in the additional timber so that there is something other than the glue joint to resist any lateral pressure that might be applied to the faceplate or glueblock. That working surface has to be cleaned up after each use, so it eventually is used up and has to be replaced - not a problem, just turn another tenon, and glue on a new face. After cutting the threads, I apply paste wax as a lubricant/preservative. Some people like to saturate the threads with thin CA, and then run the tap through again to clean them up; I don't have a problem with this but I don't think it's necessary (I've never had a threaded fitting wear out).

Second, Ed's advice to start cutting the circle on the lathe and the finish the cut on a bandsaw is fine, but you can also just treat this like a bowl where you start cutting at the outer corners of the square, and gradually turn down to create a circle. I agree that trying to simply cut a circle with a parting tool could have a dramatic ending! By the way, if the blank is plywood, then using a carbide tool makes a lot of sense - plywood can rapidly dull even high-speed steel tools.

Third, Harbor Freight sells a 5" mandrel with a permanent 'hook' surface on the face that can be used in conjunction with standard 5" hook and loop sanding disks. It comes with a 5/8" nut to mount on a 5/8" male thread. One option is to cut down a 5/8" bolt to create a shaft that can be gripped in a chuck (scroll chuck or collet chuck). My approach was to turn a wooden fitting that screws directly to my spindle (see point 1 above) with a tenon on the end that screws into the 5/8" nut. A little epoxy makes it permanent.
 
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Just to piggyback off what Louie was saying. Carpet tape as you can see here is holding that acrylic face plate as well as the block of MDF that holds the quarter that I was thinning down. This did a couple things. It kept it from wandering off and also helped center. You can easily use a live center to help support the pressure toward the faceplate because you object is larger than a quarter. It will not get in the way but if it does the tape should do fine alone. I would make the groove first to keep the support and then cut the final circle with light cuts. You can build a jig like this with scraps of wood. I happen to be using a round object so easy to drill a hole. Good luck.
 
Double sided tape did the trick. I forgot I had some high performance double sided tape that was thin (not foam based) that I'd bought from Rockler about a year ago. Taped one of the HDPE blocks to a piece of sacrificial wood, brought up the tailstock with the only flat-tipped live center I had, and was able to turn it fine. Once its stuck to something, HDPE is amazingly easy to turn. I think I turned the lip just slightly too thin, so I may have to turn another, or maybe find a way to shim this one with pieces of tape or something under the rim, not sure. But I was able to turn this to exactly the right diameter.

HDPE Zero Clearance Jet Insert-1.jpg

HDPE Zero Clearance Jet Insert-2.jpg

HDPE Zero Clearance Jet Insert-3.jpg


I think I'll be double-sided taping this to another piece of sacrificial wood so I can cut a slot about 5/8 of the way through (that seems to be where the blade sits, about 5/8 through the hole. There is also this little set screw that I believe is intended to keep the plate from twisting in the hole, so I probably need to use a square to drill a small notch 90 degrees from the slit.
 
I use double sided tape for alot of things and jigs. Have turners tape as well as the stronger carpet tape for different applications. Works well. Glad it worked out for you.
 
Got some at the recycling center a while back. A local business was tossing some that had pieces cut out. I salvaged one piece and turn bushings from it. I turned a piece round and taper one end for a bushing.
 
I've found that a very inexpensive source of HDPE is the local dollar store. Cutting boards intended for kitchen use are made of HDPE and can easily by cut into turnable chunks on the table saw (be careful and wear safety glasses - my saw throws chips into the air and HJDPE chips aren't as 'skin-friendly as wood chips).
 
So...I did turn the lip too shallow, by about 1/32nd I think. I had it exactly 1/8th at first, but I think when I was turning the diameter below the lip, I must have been shaving off bits of the lip as well.

Is it a waste of time to try and build up some layers of tape or something to recover that 1/32nd? It took a good bit to try and carve a notch for that set screw... I'd like to not have to do that again, but if its the only real way to resolve the issue, then I have 9 more 3x3 plates of HDPE to try with.
 
If it was me, I would try a few bits of blue painters tape under the lip. Then in a few days I would probably re-make it. It's just me. I always wind up even making my jigs over so I can correct all of the things that I had to patch up the first time. - Dave
 
jrista said:
I ordered some small 3" HDPE squares to make some zero-clearance plates for my Jet bandsaw. There are some third party plates on the market, but all of them seem to be 2.5" diameter, and by my caliper measure my lathe is 2.75". Additionally, the lip in the hole of my lathe is thinner than these third party plates.

I have the HDPE sheets, but I now have the problem of turning them. I've been trying to find a way to do that, and came across this video by Ed of ExoticBlanks:


His idea of using a nut bonded directly to a piece of wood is quite intriguing! The challenge I have now is, I'm having trouble getting any glue to stick...which, ironically, is kind of the point of HDPE! :p So now I'm on the hunt for a type of glue that will indeed bond to HDPE and hold it tightly enough that I could turn it round, and down to a diameter of 2.75" with a 1/8" thick lip about 3/16" wide.

Thanks!
Click to expand...
So perhaps not Scotch tape then....
but suggested as a strong type of double sided tape.
Bandsaw inserts have a fairly high attrition rate,I have made numerous by turning plywood using the tape method.
 
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